Overspeed control



Oct. 21, 1958, J. G. LEONARD OVERSPEED CONTROL Filed Oct. 10, 1955 mm Z .ibr

, IN V EN TOR. dO/l/V 6. l OW/9B0 tained concentric therewith by suitable means.

United States Patent OVERSPEED CONTROL John G. Leonard, Lynn, Mass, assignor to the United States of America as represented by the Secretary of the Air Force Application October 10, 1956, Serial No. 615,211

15 Claims. (Cl. 200-80) This invention relates to an overspeed control and, more particularly, to an explosion-proof electric switch that is automatically operated upon a predetermined condition of the mechanism with which it is associated. The switch is automatically reset when the predetermined condition is corrected.

One problem with overspeed control switches, which energize an electrical circuit when the mechanismassociated with the switch exceeds a predetermined speed, for example,'is that there is no mechanism for automatically resetting this switch after correction of the excessive speed. The present invention satisfactorily solves this problem by providing an apparatus "having an electrical switch that is automatically reset after the overspeed is corrected. 'Some overspeed control switches are employed Where it is'desired to minimize the possibilities of an explosion and the present invention satisfactorily solves this problem by employing an explosion-proof switch.

An object of this invention is to provide an overspeed switch that automatically resets after the overspeed is corrected. 7

Another object of this invention is to' provide an explosion-proof centrifugally actuated electric switch.

Other objects of this invention will be readily perceived from the following description.

This invention relates to an overspeed control for a rotating shaft or the like comprising an unbalanced ring connected to the shaft to rotate therewith. When the shaft is below a predetermined speed, the ring'is main- An annular member is disposed in the path of the ring when it becomes eccentric at a predetermined speed so that engagement of the annular member by the ring energizes an electric circuit.

This invention further relates to an explosion-proof switch including a rubber housing having a pair of spaced electrical contacts disposed therein. A member is disposed in the housing and has a portion thereof extending outside of the housing. Movement of the portion of the member extending outside the housing moves th contacts into engagement.

The attached drawing illustrates apreferred embodi- -ment of the invention, in which:

Fig. 1 is a front elevational view of a portion of the present invention connected to a rotating shaft;

Fig. 2 is a sectional view taken along the line '22 of Fig. 1;

Fig. 3 is a sectional view partly in elevationof the present invention including the explosion-proof switch; and

Fig. 4 is a side elevational view of Fig. 3.

Referring to the drawing and. particularly Fig. 1, there is shown a rotating shaft 1% of an apparatus having its speed controlled by the present invention. The shaft has a member 11 secured thereto to rotate therewith. An annular unbalanced'ring 12 is secured to the member by the ring 12 when it becomes eccentric.

11 by a pin 14 so that the annular ring 12 rotates at the same speed as the shaft 10.

Resilient means such as a coil spring 15 is secured at one end to the shaft 10 and the other end to the inner surface of the ring 12. As the speed of the rotating shaft 10 increases, the unbalanced ring 12 tends to become eccentric due to the unbalanced weight therein. However, the coil spring 15 maintains the ring 12 concentric with the shaft 10 until a predetermined speed is reached; this predetermined speed, of course, being the speed at which it is desired to energize an electrical circuit. Accordingly, the force of the spring 15 is selected so that it is able to overcome the centrifugal force of the unbalanced ring 12 until the rotating shaft 10 reaches its predetermined speed. When the shaft 113 reaches its predetermined speed, the unbalanced mass of the ring 12 produces a centrifugal force greater than the force of the spring 15 and the ring 12 becomes eccentric with respect to the shaft 10. In order to limit the eccentric movement of the unbalanced ring 12, the member 11 has a second pin 16 secured thereto and disposed in an arcuate slot 17 in the ring 12. This slot 17 is designed so that the ring 12 moves a sumcient distance when it becomes eccentric to actuate the electrical switch of Figs. 3 and 4.

As seen in Figs. 3 and 4, the switch includes a rubber housing 18 secured to a stationary housing 19. A pair of annular electrical contacts 2% and 21 is bonded with in the rubber housing 18 and spaced from each other. The contacts 20 and 21 may be manufactured by forming a single ring and then forming a gap 22 between the contacts by saw cutting the ring. This procedure insures that a constant gap 22 exists between the contacts 20 and 21 through which the contact 21 moves to engage the contact 21.

The contacts 26 and 21 are moved into engagement with each other by an annular spring 23 having a portion embedded within the rubber housing 18 and a portion extending outside of the housing 18 for engagement As will :be seen from Fig. 3, movement of the portion of the spring 23 extending outside of the rubber housing 18 produces movement of the entire rubber housing whereby the contact 20 moves through the gap 22 into engagement with the contact 21 to close an electrical circuit. The contacts 20 and 21 have leads 24 and 25 extending therefrom, respectively, to the rest of the electrical circuit (not shown). In order to provide the greatest flexibility to the spring 23, it is made of a plurality of segments rather than unitary. While flexibility would be reduced if the annular spring 23 were made of a single portion, it will be understood that such a construction could be employed, if desired. A stiffening member :26 is disposed about three sides (see Fig. 3') ofthe rubber housing 18 to add support and stiffness thereto.

Considering the operation of the present invention-it will be seen that when the rotatingshaft exceeds the .predetermined speed, the force oftheunbalancedring'12 overcomes the force of thespring 15 and the ring 12 moves into engagement with the annular spring 23. The annular spring 23 acts through the rubber housing 18 to cause engagement of the contacts 21 and 21 to close an electrical circuit. It will be understood that the closing of this electrical circuit could open another electrical circuit, if desired. As long as the rotating shaft 1% exceeds the predetermined speed, the electrical contacts 20 and remain in engagement since the contacts 20 and 21 and the spring 23 are all annular and, thus, some part of the contacts and spring are always in contact when the ring 12 is.-eccentric. As soon as the condition causing the rotating shaft 14) to exceed the predetermined speedhas been correctechthe ring 12 returns to its concentric position with respect to the shaft due to the force of the spring and engagement between the contacts and 21 is broken. This eliminates any need of a reset operation as the apparatus is automatically reset since the contacts 20 and 21 are again open and ready to be closed when the ring 12 again becomes eccentric and engages the spring 23.

While the annular spring 23 has been shown disposed in the path of the outer surface of the ring 12, it will be understood that the annular spring 23 could be designed to be disposed for engagement by the inner surface of the ring 12 when the ring becomes eccentric. Since the engagement of the annular spring 23 by the inner surface of the ring 12 would produce a radial force toward the center, it will be understood that the contacts 20 and 21 would have to be arranged to be closed by this movement. It also will be understood that the coil spring 15 may be a leaf spring, if desired.

An advantage of this invention is that it provides a steady contact between the eccentric ring and the switch contact at all times that the ring is eccentric.

For purposes of exemplification, a particular embodiment of the invention has been shown and described according to the best present understanding thereof. However, it will be apparent that changes and modifications in the arrangement and construction of the parts thereof may be restorted to without departing from the true spirit and scope of the invention.

I claim:

1. An overspeed switch for a rotating shaft including a rubber housing, a pair of electrical contacts embedded in said housing and spaced apart, a member embedded in said housing having a portion extending outside of said housing, said contacts being engaged by movement of the portion of said member extending outside the housing, and an actuating mechanism responsive to a predetermined speed of the shaft to engage the portion of said member extending outside of the housing to move the contacts into engagement.

2. An overspeed switch for a rotating shaft including a rubber housing, a pair of electrical contacts embedded in said housing and spaced apart, said housing having a gap therein through which at least one of the contacts is movable for engagement therebetween, a member embedded in said housing having a portion extending outside of said housing, said contacts being engaged by movement of the portion of said member extending outside the housing, and an actuating mechanism responsive to a predetermined speed of the shaft to engage the portion of said member extending outside of the housing to move the contacts into engagement.

3. An overspeed switch for a rotating shaft including a rubber housing, a stiffening member surrounding a portion of said housing, a pair of electrical contacts embedded in said housing and spaced apart, a member embedded in said housing having a portion extending outside of said housing, said contacts being engaged by movement of the portion of said member extending outside the housing, and an actuating mechanism responsive to a predetermined speed of the shaft to engage the portion of said member extending outside of the housing to move the contacts into engagement.

4. An explosion-proof switch including a rubber hous ing, a pair of electrical contacts completely embedded in said housing and spaced from each other, and a member embedded in said housing and having a portion extending outside of said housing, said contacts being engaged by movement of the portion of said member extending outside of the housing.

5. An explosion-proof switch including a rubber housing, a pair of electrical contacts completely embedded in said housing and spaced from each other, said housing having a gap therein through which at least one of the contacts is movable for engagement therebetween, and a member embedded in said housing and having a portion extending outside of said housing, said contacts being engaged by movement of the portion of said member extending outside of the housing.

6. An explosion-proof switch including a rubber housing, a pair of electrical contacts completely embedded in said housing and spaced from each other, said housing having a gap therein through which at least one of the contacts is movable for engagement therebetween, and a resilient member embedded in said housing and having a portion extending outside of said housing, said contacts being engaged by movement of the portion of said member extending outside of the housing.

7. An explosion-proof switch including a rubber housing, a pair of electrical contacts completely embedded in said housing and spaced from each other, said housing having a gap therein through which at least one of the contacts is movable for engagement therebetween, a stiffening member surrounding a portion of said housing, and a resilient member embedded in said housing and having a portion extending outside of said housing, said contacts being engaged by movement of the portion of said member extending outside of the housing.

8. An overspeed device comprising an unbalanced ring connected to a rotating shaft or the like, means to maintain the ring concentric with the shaft below a predetermined speed, means to limit the eccentric movement of the ring when it exceeds the predetermined speed, an annular member surrounding said ring, and a pair of annular electrical contacts adjacent the annular member, said annular member closing said contacts when the ring becomes eccentric and engages the annular member.

9. An overspeed control for a rotating shaft or the like including a rubber housing, a pair of electrical contacts embedded in said housing and spaced apart, a member embedded in said housing and having a portion extending outside of said housing, an unbalanced ring connected to the shaft to rotate therewith, and means to maintain the ring concentric with the shaft below a predetermined speed, said member disposed in the path of the ring when it becomes eccentric at the predetermined speed whereby movement of the member by engagement with the ring moves the contacts into engagement.

10. An overspeed control for a rotating shaft or the like including a rubber housing, a pair of electrical contacts embedded in said housing and spaced apart, a resilient member embedded in said housing and having a portion extending outside of said housing, an unbalanced ring connected to the shaft to rotate therewith, and means to maintain the ring concentric with the shaft below a predetermined speed, said resilient member disposed in the path of the ring when it becomes eccentric at the predetermined speed whereby movement of the resilient member by engagement with the ring moves the contacts into engagement.

11. An overspeed control for a rotating shaft or the like including a rubber housing, a pair of electrical contacts embedded in said housing and spaced apart, an annular member embedded in said housing and having a portion extending outside of said housing, an unbalanced ring connected to the shaft to rotate therewith, and means to maintain the ring concentric with the shaft below a predetermined speed, said annular member disposed in the path of the ring when it becomes eccentric at the predetermined speed whereby movement of the annular member by engagement with the ring moves the contacts into engagement.

12. An overspeed control for a rotating shaft or the like including a rubber housing, a pair of electrical contacts embedded in said housing and spaced apart, said housing having a gap therein through which at least one of the contacts is movable for engagement therebetween, a member embedded in said housing and having a portion extending outside of said housing, an unbalanced ring connected to the shaft to rotate therewith, and means to maintain the ring concentric with the shaft below a 5 predetermined speed, said member disposed in the path of the ring when it becomes eccentric at the predetermined speed whereby movement of the member by engagement with the ring moves the contacts into engagement.

13. An overspeed control for a rotating shaft or the like including a rubber housing, a pair of annular electrical contacts embedded in said housing and spaced apart, an annular member embedded in said housing and having a portion extending outside of said housing, an unbalanced ring connected to the shaft to rotate therewith, and means to maintain the ring concentric with the shaft below a predetermined speed, said annular member disposed in the path of the ring when it becomes eccentric at the predetermined speed whereby movement of the annular member by engagement with the ring moves the contacts into engagement.

14. An explosion-proof switch including a rubber housing, a pair of annular electrical contacts embedded in said housing and spaced from each other, and an annular member embedded in said housing and having a portion extending outside of said housing, said contacts being engaged by movement of the portion of said member extending outside of the housing.

15. An explosion-proof switch including a rubber housing, a pair of annular electrical contacts embedded in said housing and spaced from each other, and a resilient member embedded in said housing and having a portion extending outside of said housing, said contacts being engaged by movement of the portion of said member extending outside of the housing.

References Cited in the file of this patent UNITED STATES PATENTS 528,746 Teal Nov. 6, 1894 742,280 Blair Oct. 27, 1903 1,074,879 London Oct. 7, 1913 2,062,121 Edmunds Nov. 24, 1936 2,167,590 Slaugenhop July 25, 1939 2,212,800 Steel Aug. 27, 1940 2,367,441 Schwinn Jan. 16, 1945 2,768,255 Maddox Oct. 23, 1956 

